package practice.tmp;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

public class Solution18 {
    public List<List<Integer>> fourSum(int[] nums, int target) {
        Arrays.sort(nums);
        List<List<Integer>> res = new ArrayList<>();
        for (int i = 0; i < nums.length; i++) {
            if (nums[i] > 0 && nums[i] > target) break;
            if (i > 0 && nums[i] == nums[i - 1]) continue;
            for (int j = i + 1; j < nums.length; j++) {
                if (j > i + 1 && nums[j] == nums[j - 1]) continue;
                int left = j + 1;
                int right = nums.length - 1;
                while (left < right) {
                    if (nums[i] + nums[j] + nums[left] + nums[right] == target) {
                        List<Integer> tmp = new ArrayList<>();
                        tmp.add(nums[i]);
                        tmp.add(nums[j]);
                        tmp.add(nums[left]);
                        tmp.add(nums[right]);
                        res.add(tmp);
                        while (left < right && nums[left] == nums[left + 1]) left++;
                        while (left < right && nums[right] == nums[right - 1]) right--;
                        left++;
                        right--;
                    } else if (nums[i] + nums[j] + nums[left] + nums[right] < target) left++;
                    else right--;
                }
            }
        }
        return res;
    }
}
